Method of composing signatures

ABSTRACT

The present invention provides a method of electronic composition for electronically ordering logical pages onto physical pages printed by a printer. The first step is to determine the number of physical pages in a signature, and the pattern in which two or more logical pages will be imposed on the physical page. Based on the pattern, a seed table is selected having an entry for each position of the pattern. The logical pages are then electronically ordered by assigning a logical page to each position of each physical page based on the place of each physical page in the sequence of physical pages and based on the entry in the seed table corresponding to the pattern position contemplated.

BACKGROUND

This invention relates to electronic composition, and more particularlyto a method of composing signatures.

The raw materials of electronic composition are text and image data thathave not been paginated or otherwise composed. The electroniccomposition process groups or paginates the data as logical pages, withone or more logical pages destined to be printed by a printer on aphysical page. After printing, the physical pages will be folded andassembled into signatures.

Present methods of electronic composition determine how to print two ormore logical pages in sequence on each physical page by consultinglook-up tables, stored in memory. These look-up tables are little morethan electronic versions of the tables, derived empirically, that offsetprinters have used for years to manually compose signatures on offsetpresses. While generally adequate for electronic composition, look-uptables are inflexible and cumbersome, requiring unique entries for eachpossible combination of number of physical pages and pattern of logicalpages on each physical page.

SUMMARY OF THE INVENTION

The present invention provides a method of electronic composition forelectronically ordering logical pages onto physical pages printed by aprinter. The first step is to determine the number of physical pages ina signature, and the pattern in which two or more logical pages will beimposed on the physical pages. Based on the pattern, a seed table isselected having an entry for each position of the pattern. The logicalpages are then electronically ordered by assigning a logical page toeach position of each physical page based on the place of each physicalpage in the sequence of physical pages and based on the entry in theseed table corresponding to the pattern position contemplated. The stepof assigning logical pages to the positions of physical pages includesthe step of determining whether the corresponding seed table entry ispositive, and assigning logical pages based on the following algorithm:##EQU1##

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an example of two-up signature printingformed by the method of the present invention, with two folded papersheets being nested to form a signature;

FIG. 2 is a schematic diagram illustrating the seed table and assignmentof logical pages onto physical pages for the example of FIG. 1;

FIG. 3 is a schematic diagram showing a first example of four-upsignature printing according to the method of present invention;

FIG. 4 is a schematic diagram showing a second example of four-upsignature printing according to the method of present invention;

FIG. 5 is a schematic diagram showing a printer performing the two-upsignature printing of the example in FIGS. 1 and 2; and

FIG. 6 is a flow chart describing the steps used to implement the methodof the present invention for the examples as shown in FIGS. 1 through 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention will hereinafter be described in connectionwith a preferred embodiment, it will be understood that it is notintended to limit the invention to that embodiment. On the contrary, itis intended to cover all alternatives, modifications, and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims.

Referring now to FIGS. 1, 2, and 5 there is shown an example of two-upsignature composition: eight logical pages 4 are assigned positions onfour physical pages 2. Two logical pages 4 are positioned in a side byside pattern on each physical page 2. One physical page 2 constitutes aside (i.e., front or back side) of a paper sheet 6. Of course, sheet 6could be any medium suitable for receiving print (e.g., plastic). Aftera printer (not shown) prints logical pages 4 onto physical pages 2,paper sheets 6 will be folded and assembled as shown in FIG. 1 to form asignature 8.

In accordance with the invention, the logical pages 4 are assigned tophysical pages 2 based on the place of each physical page 2 in thesequence of physical pages 2 and based on an entry 10 in a seed table12. Seed table 12 has a pattern of entries 10 that matches the patternof positions of logical pages 4 on a physical pages 2. The entry 10 usedis the one that corresponds to the position of the logical page 4 on thephysical page 2. Moreover, each seed table 12 consists of a front seedtable 12-1 and a back seed table 12-2, to be used with physical pages 2that are positioned on the front and back sides, respectively, of apaper sheet 6. In particular, the method of the invention determines thelogical page 4 that should be assigned to a particular position on aphysical page 2 y first determining whether the corresponding seed tableentry 10 is positive, and then performing the following calculation:##EQU2##

For example, the logical pages 4 assigned to the front physical page 2-1of the first paper sheet 6-1 are determined as follows, using front seedtable 12-1:

    ______________________________________                                        LEFT POSITION                                                                              Logical page = abs(-2) * 4 - 0 = 8,                                           for logical page 4-8; and                                        RIGHT POSITION                                                                             Logical page = (+1) * 4 - 3 = 1,                                              for logical page 4-1.                                            ______________________________________                                    

Referring now to FIG. 3, there is shown an example of four-up signatureprinting in which four logical pages 20 are positioned on each of eightphysical pages 22. The physical pages 22 are part of four paper sheets24. Logical pages 20 are assigned to physical pages 22 using the aboveequation together with seed table 26. Paper sheets 24 are assemble andfolded to form a signature (not shown) by first stacking the papersheets 24 in order from top to bottom with paper sheet 24-1 havingphysical page 22-1 on top, and with paper sheet 24-4 having physicalsheet 22-8 on bottom. Then the stack of paper sheets 24 is foldedhorizontally downward, leaving logical pages 20-32 and 20-1 of physicalpage 22-1 on top. Finally, the stack of paper sheets 24 is foldedvertically, leaving logical page 20-1 on top as the first logical page20, and leaving logical page 20-32 on bottom as the last logical page20.

Referring now to FIG. 4, the utility of the method of the invention isshown by another example of four-up signature printing. Here, fourlogical pages 28 are positioned on each of four physical pages 30. Thephysical pages 30 are part of two paper sheets 32. The same seed table26 used in the example of FIG. 3 can be used, since the pattern oflogical pages 28 on physical pages 30 is the same as the pattern oflogical pages 20 on physical pages 22, and since a signature (not shown)is to be formed by folding the paper sheets 32 in the same manner aspaper sheets 24 were folded.

In recapitulation, referring now to FIGS. 1, 2, 5 and 6, the presentinvention provides a method for ordering logical pages onto physicalpages. The first step 100 is to determine the number of physical pages 2in a signature 8, and the pattern in which two or more logical pages 4will be imposed on each physical page 2. Based on the pattern, in thenext step 102 a seed table 12 is selected having an entry 10 for eachposition of the pattern. In step 104 the logical pages 4 are thenordered by assigning a logical page 4 to each position of each physicalpage 2 based on the place of each physical page 2 in the sequence ofphysical pages 2 and based on the entry 10 in the seed table 12corresponding to the pattern position contemplated. Finally, in step 106printer 1 prints logical pages 4 in the assigned positions on physicalpages 2. As is well known to those skilled in the art, the method of thepresent invention operates in conjunction with a control program, whichis a specific designed sequence of instructions that guides the computer(not shown) of printer 1 through the various operations that wouldotherwise have to be put into each individual program. Manymodifications and variations are apparent from the foregoing descriptionof the invention and all such modifications and variations are intendedto be within the scope of the present invention.

I claim:
 1. A method of electronic composition for electronicallyordering logical pages onto physical pages printed by a printer,comprising the steps of:a) determining the number of physical pages in asignature and the pattern in which logical pages will be imposed on thephysical pages; b) based on the pattern determined in step a, selectinga seed table having an entry for each position of the pattern; c)electronically ordering the logical pages by assigning a logical page toeach position of each physical page based on the place of each physicalpage in the sequence of physical pages and the entry in the seed tablecorresponding to the pattern position contemplated, by first determiningwhether the corresponding seed table entry is positive, and then byassigning logical pages based on the following algorithm: ##EQU3## d)printing the logical pages in the assigned positions on the physicalpages.